Generally, in wireless communication apparatuses, various modulation methods are used, such as ASK modulation in which the amplitude of a carrier wave is modulated in accordance with an ASK data signal, and QPSK modulation in which the phase of a carrier wave is modulated into four phases using an I-signal (in-phase signal) and a Q-signal (quadrature signal) in accordance with a QPSK data signal.
In a known wireless communication apparatus, modulators in accordance with both of the modulation methods, such as an ASK modulator and a QPSK modulator, are attached, and each modulator, together with a high-frequency signal source for supplying a carrier wave, a mixer for mixing a reception wave and a carrier wave for receiver detection, etc., constitutes an RF unit for handling high-frequency signals.
In the wireless communication apparatus according to the related art described above, in order to allow both ASK modulation and QPSK modulation, two RF units must be provided in the single wireless communication apparatus in accordance with the two modulation methods, respectively.
That is, an RF unit for ASK modulation and an RF unit for QPSK modulation must be separately provided, which incurs a higher manufacturing cost compared with a wireless communication apparatus having only one of the modulation functions. In particular, if the high-frequency signal source, the mixer, etc. are implemented using expensive ICs composed of GaAs, etc., the manufacturing cost is considerably raised. In addition, because two RF units are provided, the RF units have a larger footprint and occupy a larger space, increasing the overall size of the wireless communication apparatus.
Addressing these concerns, the present invention provides a wireless communication apparatus which is capable of both ASK modulation and QPSK modulation, which can be manufactured at a low cost, and which is small in size.